Temperature indicating device and composition for use therein

Abstract

 A composition for use in a reversible thermometer comprising a thermally responsive material capable of being supercooled for several minutes, and of changing state from solid to liquid at a predetermined temperature, means for visually observing the change in state, and a matrix forming material in which the thermally responsive material is dispersed, the matrix material comprising an amorphous organic compound, and being insoluble in the thermally responsive material. A suitable matrix material is polyisobutylene, and a suitable thermally responsive material is a solid solution of ortho-chloronitrobenzene and ortho-bromonitrobenzene.

Description

[0001] This invention relates to a composition for use in a reversible thermometer, to a temperature indicating device, and to a process of making a composition for use in a thermometer. The composition can be used in a clinical thermometer which holds its signal for a time sufficient to be read, but reverses to its original condition thereafter.

[0002] US-3946612 discloses a clinical thermometer comprising a plurality of cavities filled with solid solutions of two thermally responsive materials in each pocket. The melting point of the contents of each pocket varies as a result of the ratio of the two compounds in each pocket. The compositions are compounded to cover the clinical temperature range in 0.36°C (0.2°F) increments. The preferred thermally responsive material comprises a solid solution of ortho-chloronitrobenzene and ortho-bromonitrobenzene (OCNB and OBNB respectively).

[0003] The composition disclosed in US-3946612 is subject to a supercooling phenomenon. Upon melting the composition remains in the liquid state long after the composition has been brought to a temperature below its melting point. For the thermometers of the type contemplated by the prior art, this presents problems, and means have been devised to cause the compositions to solidify rapidly upon being cooled below their melting point.

[0004] US-3980581 discloses compositions useful as nucleating agents in the OCNB/OBNB solid solutions of the prior art. These nucleating agents are salts of metals and include sodium borate, cryolite, sodium acetate and cobalt chloride.

[0005] The nucleating agents referred to in US-3980581 are effective but are subject to a "poisoning" effect. As the thermally responsive materials subjected to melting and resolidification cycles, the nucleating agent pores eventually becomes filled with the thermally responsive material. As a result, the nucleating agent became ineffective. This "poisoning" problem is solved by the invention disclosed in US-3956153. This document discloses a regenerative nucleating agent comprising a compound which is sparingly soluble in the thermally responsive material. Although a small amount of material dissolves into the thermally responsive material when it melts, sufficient undissolved material remains to act as a nucleating agent. Because the nucleating agent is sparingly soluble, its surface is continually regenerated, and no poisoning effect is observed.

[0006] US-4397570 discloses a disposable thermometer similar to that of disclosed in US-4232552 which utilizes a pressure sensitive adhesive containing a nucleating agent to make a thermometer which is reversible and maintains its signal for about 3 to 5 minutes. The adhesive utilized is a polyisobutylene adhesive of the type disclosed in US-4189942. The nucleating agents are generally mineral type compositions such as talc, gibbsite, calcium aluminate, etc.

[0007] US-4248089 discloses a reversible thermometer in which the temperature sensitive material comprises a combination of high molecular weight fatty acids. A nucleating agent which both allows the thermometer to be reversible and at the same time hold its signal for a reasonable period of time to be read is included. Suitable nucleating agents include dyes such as Auramine, Acridine Yellow, Red, and Orange; Rhodamine and Sudan Black.

[0008] US-4299727 discloses a reversible thermometer utilizing a heat sensitive composition, preferably as disclosed in US-4232552, comprising a matrix forming amorphous material and a film forming material which is more crystalline than the matrix forming compound. The heat sensitive composition can be a ortho-chloronitrobenzene (OCNB), ortho-bromonitrobenzene (OBNB), 1-thymol, 2-naphthol and naphthaline. The matrix forming amorphous material can comprise microcrystalline waxes and polyisobutylene. Suitable film forming materials include high melting aliphatic alcohols. Optionally, a solubilizing material such as docosanol can be included. The preferred heat sensitive composition is a combination of OCNB and OBNB.

[0009] US-4150572 discloses a reversible thermometer in which the signal is maintained for a reasonable period by the addition of a polymer to a thermally sensitive material. The preferred thermally sensitive material is a combination of OCNB and OBNB. The polymer must be soluble in the thermally sensitive material at a level of about 10 to 75 wt % based on the thermally sensitive material at the melting point of the thermally sensitive material. Suitable polymers include thermoplastic polymers such as polystyrene, polyacrylates and polyvinyl butyral.

[0010] Presently, the only commercially available chemical type thermometer utilizing the solid solutions of the type disclosed in US-3949612 is a device as disclosed in US-4232552. While the document discloses compositions utilizing the prior art nucleating agents, the device being marketed contains no nucleating agent. That thermometer relies on the supercooling effect to give a signal which is retained for a time sufficient to be read. Since the thermometer is sold as a single use devise, reversal of the signal is not required. Use of the prior art nucleating agents, however, results in a reversal which is too rapid for use where the device is to be read after it is removed from the heat source, the mouth for example. In order for the device disclosed in US-4232552 to be reusable, it must revert to its original solid state in a reasonable amount of time while at the same time hold a signal to be read for a time sufficient to permit the user to read the temperature shown.

[0011] The present invention provides a composition for a reversible thermometer which comprises a matrix of an amorphous organic compound in which a thermally sensitive material is insoluble at the temperature to be indicated by the thermally sensitive material.

[0012] Accordingly, in one aspect, the invention provides a composition of matter suitable for use in a reversible thermometer comprising:

(a) a thermally responsive material capable of being supercooled at least for several minutes, and subject to a change in state from a solid to a liquid substantially at a predetermined temperature;

(b) means for visually observing the change in state; and

(c) a matrix forming material comprising an amorphous organic compound, the matrix forming material being insoluble in the thermally responsive material;

the thermally responsive material being dispersed within the matrix forming material, and the composition of matter being reversibly responsive to changes in temperature and remaining in the liquid state for a time sufficient to permit a user of the composition to observe the change in state.

[0013] The preferred thermally sensitive material is a solid solution of o-chloronitrobenzene (OCNB) and o-bromonitrobenzene (OBNB). The matrix forming amorphous material is preferably a polymer, for example polyisobutylene.

[0014] In other aspects, the invention provides a process for dispersing the thermally responsive material in the matrix forming material of the composition of the invention, and a temperature indicating device which comprises a heat conducting carrier having a multiplicity of spaced regions defined therein to determine a like number of predetermined temperatures in a predetermined temperature range, the spaced regions containing a like number of different compositions of matter therein, the carrier having a transparent cover sheet means in sealing engagement therewith, the compositions of matter being as discussed above.

[0015] The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a partial elevation view of a flat or graduated curved prior art heat-conducting carrier having a cavity defined therein, which cavity forms an enclosure for a temperature sensitive "classical" composition of matter therein when such cavity is covered by a transparent cover sheet means in sealing engagement with carrier means overlaying the heat conducting carrier means and above the cavity;

Figure 2 is a partial plan view of a device over a part of the clinical range of temperatures embodying principles referred to in US-4232552, in degrees Celsius;

Figures 3A and 3B are, respectively, a plan view of a prior art flat temperature indicating device comprising a heat conducting carrier means with a grid of cavities thereon; and an elevation view taken along line 13-13 in FIG. 3A revealing the heat conducting carrier means within transparent cover sheet means and a bottom plate means;

Figure 4 is a cross-sectional view of a flat or gradually curved heat conducting carrier having a cavity defined therein, where a cover layer is bonded to a carrier layer by a pressure sensitive adhesive layer comprising polyisobutylene (PIB):

This invention relates to chemical type thermometers. In particular it relates to reversible clinical thermometers of the chemical type. Chemical thermometers are those thermometers which use a normally solid chemical (organic) compound as the temperature sensitive material instead of mercury or other liquid materials.

[0016] Specifically this invention relates to method and composition for preparing a reversible thermometer of the chemical type. Generally, clinical chemical thermometers require that the thermally sensitive materials be subject to some degree of supercooling so that the user will have sufficient time to read the thermometer after it is removed from the patient. Super-cooling refers to the phenomenon which maintains a normally solid material in the liquid state after it has been melted and its temperature is reduced below its melting point. While any chemical thermometer may be used in the practice of this invention so long as the criteria described herein are met, the preferred chemical type thermometer is that of the type disclosed in US-4232552, as discussed in more detail below.

[0017] Throughout the description below, the terms "novel thermally-responsive substance", "novel thermally-responsive material", "novel temperature-indicting compositions of matter", "novel temperature-sensitive solid solutions", "novel temperature-indicating solid solutions", and "novel solid solutions", or variations thereof, are used interchangeably to denote the same novel materials disclosed in US-4232552. Otherwise, the term "compositions of matter" or "classical compositions of matter" are used interchangeably to denote compounds which change only from being opaque to transparent with a corresponding change from the solid to liquid state, or vice versa.

1. Compositions of Matter

[0018] US-4232552 discloses that certain organic compounds (to be described below) form solid solutions which undergo a change in state from solid to liquid at precise and predetermined temperatures with a corresponding change in colour visible to the naked eye, and likewise, form liquid solutions which undergo a change in state from liquid to solid at a predetermined temperatures with a corresponding change in colour visible to the naked eye. The term "solid solution" is well known and usually refers to a homogeneous solution of one solid in another. The solid solutions contemplated in the present invention are composed of two or more, preferably three or four, different organic compounds with varying proportions of at least two compounds which form a solvent for the solution. Each solid solution undergoes a rapid change of state at a predetermined temperature or substantially thereabouts. By a "change in colour visible to the naked eye" of a source we mean a change in the wavelength of luminous flux of light (from the source distributing or reflecting such energy in the region of the Electromagnetic Spectrum from about 390 nm to about 760 nm (3900 Å to 7600 Å) before or after the change, or preferably both) visible to a person of normal vision and eyesight wherein the intensity of the luminous flux surrounding the source is more than or about 53 lux (5 lumens.ft⁻²). In most instances, this change in the wavelength of luminous flux to the eye will be at least about 17.5 nm (175 Å), and preferably at least about 50 nm (500 Å).

[0019] Preferably, when a small but effective amount (generally a weight fraction from about 0.005 to 0.2 weight percent, and generally about 0.05 weight percent of the entire composition, but the optimum may be more or less upon experimentation, depending on the below described Group I-III compounds, selected and the solvent selected, up until both phases appear dark, appear the same colour, or the melting point becomes too broad for the use desired - some latitude for experimentation is present here) of one or more of Group III compounds comprising: pinacyanol iodide, 1,1'-diethyl-2,2'-cyanine iodide, quinaldine red, pinacyanol chloride, thionin, methylene blue, cresol red, chlorophenol red, neutral red iodide, neutral red chloride, crystal violet, acridin orange, Orasol Orange RLN™, Orasol Navy Blue™, Irgalith Red PR™, Fat Red BS™, Xylene Cyanol FF™, Rhodamine B, Rhodamine 6G™, Irgalith Magenta TCB™, Irgalith Pink TYNC™, Toluidin Blue O™, Savinyl Green B, Savinyl Blue RS™, purpurin, 3.3''-diethyl-thiadicarbocyanine iodide, cryptocyanine, Dicyanine A™, Merocyanine 540™, 4-(p-ethoxyphenylazo)-m-phenylene diamine monohydrochloride, Yellow Orange S™, Chrysoidin G™, fuchsin, aurintricarboxylic acid (ammonium salt), Victoria Blue R™, Pyronin G™, gallein, Erythrosin Yellowish Blend™, chlorophenol blue, bromophenol blue, bromocresol purple, Coriphospine O™, acriflavin, acridine orange, rhoduline violet, Alizarin cyanin 2 R™, Alizarin Red S™, alcannin, Aurantia™, Direct Green G™, Fast Red Salt 3GL™, Fast Blue Salt BB™, Fast Garnet Salt GBC™, Carta Yellow G 180 o/o Murexide, Savinly Blue GLS™, Irgalith Blue GLSM™, phthalocyanine, Di Amingreen B™, Alizarin Blue S, Celiton Blue Extra™, neocyanine, Janus Green™, dimethyl yellow, Fast Yellow, Methyl red sodium salt, Alizarin yellow R™, Eriochrome black T™, Chromotrope 2R™, Ponceau 6R™, Brilliant Ponceau G/R/2R™, chromolan yellow, Sudan red B™, Bismarck brown G™, Fat Black™, Resorcin Brown™, Benzofast pink 2 BL™, Oil Red EGN™, Euroglaucine, Fuchsin NB™, parafuchsin, Patent Blue™, Irgalith Blue TNC™, Phloxin B™, fluorescein sodium salt, Rhodamine B base™, Eosinscarlet, Eosin Yellowish™, Erythrosin extrabluish, 4,5-dibromofluorescein, ethyleosin, Phloxine™, Cyanosin B™, chlorocresol green, pinacyanol bromide, 2-(p-dimethylaminostyryl)-1-ethyl pyridinium iodide, ethyl pyridinium iodide, ethyl red, nigrosine, savinyl blue B™, Orasol Blue BLN™, Safranin O™, Solophenyl Brilliant Blue BL™, Nile Blue A™, gallocyanine, gallamine blue celestine blue, methylene green, Azure A/B/C™, Blue VIF™, Organol™, Alizarin, Nitrofast Green GSB™, quinalizarine, Oil Blue N™, Solvay purple, Ciba Blue™, Indigo synthetic™, Chromophtal Bordeaux RS™, Acid Alizarin Red B™, 5-aminofluorescein, Rose Bengal™, Martius Yellow™, Chicago Blue 6B™, Alcian blue 8GX™, cresyl violet, 4,4'-bis(dimethylamino)benzylhdrol, Zinc Pthalocyanine, Sudan III™, Pyronin Y™, Toluylene Blue™, Cresyl Violet perchlorate, Mendola's Blue™, 3,3'-diethylthiadicarbocyanine iodide, Phosphine Dye™, Nitron™, cresyl violet acetate, Ceres Orange R™, 4-phenylazo-1-naphthylamine, 4-(4-dimethylamino-1-naphtylazo-3-methoxybenzene sulphonic acid, Bindschedler's Green™, and p-(p-dimethylaminophenylazo)benzoic acid, or one of the other organic moieties to be described (one or more Group I compounds with one or more Group II compounds) is combined with a suitable solvent, for example, a pure mixture of ortho-chloronitrobenzene (OCNB) and ortho-bromonitrobenzene (OBNB) for use in clinical applications. The temperature of the change of state of a number of solid solutions with a corresponding change in colour may be accomplished at approximately 0.1°C (0.2°F) intervals, i.e. a change of state of one temperature-sensitive composition of matter at a temperature 0.1°C (0.2°F) different from the temperature of chance in state of another novel composition of matter in an adjacent region containing another proportion of the same organic moieties in ortho-chloronitrobenzene and ortho-bromonitrobenzene. Thus, for example, in human clinical applications where temperature measurements in the range from 35.5°C to 40.5°C (96°F to 105°F) are usually desired, 45 to 50 different solid solutions differing in their percentage compositions but otherwise made from the same two components) will provide all of the necessary temperature gradations at increments of 0.1°C (0.2°F), that is 35.5°, 35.6°, 35.7°, etc upto and including 40.4°C (96.0°, 96.2°, 96.4°, etc upto and including 104.8°F). The solution of ortho-chloronitrobenzene and ortho-bromonitrobenzene, when the ortho-bromonitrobenzene varies from 56.2 weight percent to 96.0 weight percent, provides an excellent starting mixture for determination of temperatures in the human clinical temperature range. Usually the addition of the Group I-III organic moieties (hereinafter sometimes "organic moieties") consisting of a small but effective percentage of one or more of the aforesaid Group III compounds, or a combination of one or more Group I compounds with one or more Group II compounds affects the temperature curve of the solid solution by only a small increment which is substantially constant along the entire curve. Regardless of the solvent system selected for a given predetermined temperature range, it is necessary that the organic moieties selected for the colour change constitute a small but effective amount of moieties, e.g. at least that amount sufficient to provoke a colour change visible to the naked eye, and preferably up to a saturated solution of Group I-III organic moieties, and most preferably about 0.005 to about 0.2 weight percent of an inert, preferably aromatic solvent constituents, constituting the remaining balance of the mixture. The Group I-Group III moieties may in some instance exceed 0.2 weight percent as long as the melting point remains sharp and both phases are not so dark as to eliminate a colour change visible to the naked eye. If too small an amount of organic moieties is employed, the colours and the colour change are too faint under weak light; if too large an amount is employed, the colours are too dark and the colour change is harder to visualize and there is a possibility that the sharpness of the melting point will be affected. It is also noted that the organic moieties and suitable solvent to be described should be substantially free of impurities, generally, such impurities should be kept less than 0.3% of the entire composition. Supersaturated solutions are not preferred for reasons to be enumerated below.

[0020] The dye systems (organic moieties) referred to in US-4232552 are useful in the practice of this invention, and are incorporated into the solid solutions at a preferred concentration about 0.03 wt % to about 0.15 wt % based on the weight of solid solution plus organic moiety; more preferably at about 0.035 to about 0.1 wt %. Once a proposed solvent system has been selected (consisting of one or more compounds) for the temperature(s) to be determined, the compound(s) of the system must be tested for the Group I-III moieties for stability (i.e. inertness) and solubility of the Group I-III moieties in the compound(s) of the solvent. This will be done by routine testing. Only after the solvent system compound(s) are shown to dissolve the Group I-III moieties and be inert towards them, can such a solvent system be suitable for use in the composition of the invention.

[0021] It will be appreciated that organic compounds, unlike crystalline materials, exhibit a melting point range rather than a sharp melting point. For example the OCNB and OBNB exhibit a melting point range of about 1.1°C (2.0°F). Temperature readings of within about 0.1°C (0.2°F) are achieved by selecting completion of melt temperature differentiated from one another by the incremental reading desired.

[0022] While sometimes under fortuitous circumstances the solvent system may consist of only one compound, in most instances the temperature to be determined will not be readily obtainable without mixing two or more organic compounds for the solvent system. Hence, for a temperature-indicating device, two or more related organic compound constituents in the solvent are especially helpful for measuring forty or more temperatures located at regular increments.

[0023] The selection of one or more inert solvents towards the organic moieties for use in the composition of matter will require careful scrutiny since not all organic compounds are useful for this purpose and many may fall outside a desired temperature range. A suitable solvent may be any solvent which is inert towards the organic moieties and in which the organic moieties are soluble while the solvent is in the liquid phase. In some instances, simple alcohols and other organic substances may be suitable rather than aromatic compounds. The organic compounds which are particularly adapted for the formations of solid solutions which can serve a temperature-indicating composition in accordance with the present invention are generally those which are weakly polar (e.g. compounds which are immiscible in water and have a dielectric constant less than about 35) or moderately polar aromatic organic compounds, as well as the requirements of organic moiety solubility and inertness towards the organic moieties. Thus, it has been discovered that weakly polar or moderately polar aromatic organic compounds, which have analogous chemical structures (e.g. analogues, homologues and optical isomers), have substantially the same molecular volume or have similar crystalline structures (e.g. isomorphous) and which form the solid solutions useful for solvent system constituents in preparing a grid of composition of matter to be used in predetermined temperature range for the determination of a temperature falling within said range. In addition, it is preferable that the solvent solutions have a linear or a substantially linear temperature composition liquidous curve, particularly over the desired temperature range such as, for example, over the human clinical temperature range.

[0024] Exemplary weakly polar or nonpolar aromatic solvents are ortho-chloronitrobenzene, ortho-bromonitrobenzene, naphthalene, 2-ethoxybenzamide, 1-thymol, 2-naphthol, ortho-iodonitrobenzene, meta-iodonitrobenzene, para-iodonitrobenzene, para-dibromonitrobenzene and para-toluic acid. It must be emphasized, of course, that a suitable solvent useful for one selection of organic moieties may not be useful for another, and that an operable solvent at one temperature range may not work at a different range. It is recommended that for a given temperature to be measured, one may start his investigation for the appropriate temperature(s) to be determined a suitable solvent system selected from compounds from the following:

(1) moderately polar or weakly polar aromatic compounds, i.e. compounds having a dielectric constant of less than about 35;

(2) water; or

(3) aromatic and aliphatic compounds other than those in groups (1) and (2) which are appropriate for the temperatures to be determined, and which are "inert" to the Group I-III dyes.

[0025] The constituents of the compositions of matter comprise:

(1) a solvent (I) consisting of a single substance or a mixture of substances and adapted to change from a solid state at substantially a predetermined temperature to a liquid state and

(2) an indicator system (II) consisting of one or more substances different from (I), characterized in that

(a) (II) is soluble in (I) when the latter is in the liquid phase, and

(b) (II) changes colour visible to the naked eye when (I) passes from the solid to the liquid phase or from the liquid to the solid phase.

[0026] It is well within the range of knowledge of those skilled in the art to find for a given temperature range to be measured, and for colour change desired (choosing from the various Group I-III compounds) a suitable solvent, i.e. one which is inert toward the Group I-III compounds and for which the latter a soluble in the liquid phase to said solvent.

[0027] The solid solutions made from ortho-chloronitrobenzene and ortho-bromonitrobenzene have been found to be most preferable for use in temperature measurements in the clinical range within the aforesaid accuracy. Of course, as it will be readily understood by those skilled in the art, any two or more aromatic solvents as defined above in which the organic moieties to be described below are soluble, stable and inert, may be employed for thermometers if adaptable to the temperature range to be tested, and if capable together of forming a homogeneous solid solution.

[0028] Preferably the composition of matter consists essentially of:

(A) a suitable solvent adapted to change from a solid state at a predetermined temperature to a liquid state, and

(B) an effective amount of one or more suitable organic moieties soluble in said solvent in the liquid state and adapted to change the colour of the composition visible to the naked eye upon the change of state of the solvent at substantially the predetermined temperature and selected from one or more of the group consisting of

(1) a group III body of single compounds consisting of the cyanine class of dyes, suitable dyes from the following classes: monoazo, diazo, triarylmethane, xanthene, sulphonephthalein, acridul, quinoline, azine, oxazine, thiazine, anthraquinone, indigold, and the following individual compounds: Aurantia™, Orasol orange RLN™, Diamin green B™, Direct green G™, Fast red salt 3 GL™, Fast blue salt BB™, Fast Garnet salt GBC™, Carta Yellow G 180 o/o™, Murexide, Savinyl blue GLS, Irgalith blue GLSMv, Phthalocyanine and Alcannin,

(2) mixtures of:

(a) one or more organic acids compounds, having a pK of less than about four, and

(3) mixtures of

(a) one or more organic acids having a pK of less than about 2 and

(b) one or more acid dyes or acid indicators

(4) mixtures of

(a) one or more organic acid compounds having a pK of less than about 4 and

(b) one or more members of the group I body of compounds,

(5) mixtures of

(a) one or more basic dyes or basic indicators and

(b) one or more members of the group I body of compounds,

(6) mixtures of

(a) one or more dyes having a molecular structure containing a lactone group, and

(b) one or more acids having a pK of about 8 to about 12.

[0029] The compounds mentioned in group III are classified according to the Colour Index, 3rd Edition (1971), published by the Society of Dyers and Colourists, Great Britain and Conn's Biological Stains (9th Ed 1977).

[0030] Suitable monoazo dyes include: 4-(p-ethoxyphenylazo)-m-phenylene-diamine monohydrochloride, Orasol Navy Blue™, Organol Orange, Janus Green™, Irgalith red P4R, Dimethyl yellow, Fast Yellow, Methyl red sodium salt, Alizarin Yellow R-, Eriochrome Black T, Chromotrope 2R, Ponceau 6R, yellow Orange S™, Brilliant Ponceau 5R™, Chrysolidin G™, Eriochrome black A, Benzyl orange, Brilliant ponceau G/R/2R™ and chromolan yellow.

[0031] Suitable diazo dyes include: Fat red BS™, Sudan Red B™, Bismarck Brown G™, Fat Black™, Resorcin Brown™, Benzofast Pink 2 BL™ and Oil Red EGN™.

[0032] Suitable triarylmethane dyes include: Methyl violet, Xylene cyanol FF™, Erioglaucine™, Fuchsin NB™, Fuchsin, Parafuchsin, Aurintricarboxylic acid Ammonium salt, Patent Blue, Victoria blue R™, Crystal violet and Irgalith Blue TNC™.

[0033] Suitable xanthene dyes include: Phloxin B, Fluorescein sodium salt, Rhodamine B, Rhodamine B Base™, Rhodamine 6G™, Pyronin G, Irgalith Magenta TCB™, Irgalith Pink TYNC™, Eosin Scarlet™, Eosin Yellowish, Erythrosin extra bluish™, 4'5'-Dibromofluorescein, Ethyl eosin, Gallein, Phloxine™, Erythrosin yellowish Blend™ and Cyanosin B™.

[0034] Suitable sulphonephthaleins include cresol red, chorophenol red, chlorophenol blue, bromophenol blue, bromocresol purple and chlorocresol green.

[0035] Suitable acridine dyes include: Corisphosphine O™, Acriflavine and acridine orange.

[0036] Particularly preferred quinoline dyes include: pinacyanol chloride, pinacyanol bromide, pinacyanol iodide, quinaldine red, cryptocyanine, 1,1'-diethyl-2,2'-cyanine iodide, 2-(p-Dimethylaminostyryl)-1-ethyl-pyridinium iodide, 3,3'-diethylthiadicarbocyanine iodide, ethyl red, Dicyanine A, Merocyanine 540 TM and Neocyanine™.

[0037] Suitable azine dyes include: Neutral red chloride, Neutral red iodide, Nigrosine™, Savinyl blue B™, Orasol blue BLN™, Safranin O ™, Azocarmin G™, Phenosafranine™, Azocarmine BX™ and Rhoduline violet.

[0038] Suitable oxazine dyes include: Solophenyl Brilliant Blue BL™, Nile blue A™, Gallocyanine™, Gallamine Blue™ and Celestine blue.

[0039] Suitable dyes include: Methylene blue, Thinonin Toluidine Blue O, Methylene Green and Azure A/B/C™.

[0040] Suitable anthraquinone dyes include: Savinyl Green B™, Savinyl Blue RS, D+C Green 6™, Blue VIF Organol™, Alizarin, Alizarin Cyanine 2R™, Celliton Blue Extra™, Alizarin Blue S™, Nitro Fast Green GSB, Alizarin red S, Chinalizarin, Oil Blue N, Solvay Purple™ and Purpurin™.

[0041] Suitable indigold dyes include: Ciba Blue™, Indigo Synthetic™, Chromophtal Bordeaux RS™ and Thioindigo red.

[0042] Alternative designations for compounds referred to in this specification are as follows, the colour index name being taken from The Color Index, published by The Society of Dyers and Colourists and the American Association of Textile Chemists and Colorists, 2nd edition, 1956 1963:

Trade mark	Colour index name
Nile Blue A	Basic Blue 12
Oil Blue N	Solvent Blue 59
Indigo Synthetic	Vat Blue 1
Fat Red BS	Solvent Red 24
Fast Garnet Salt GBC	Azoic Diazo Component 4
Fast Red Salt 3GL	Azoic Diazo Component 9
Fast Blue Salt BB	Azoic Diazo Component 20
Rhodamine 6G	Basic Red 1
Rhodamine B Base	Solvent Red 49
Rose Bengal	Acid Red 94
Savinyl Green B	Solvent Green 19
Savinyl Blue RS	Solvent Blue 45
Savinyl Blue GLS	Solvent Blue 44
Sudan Red B	Solvent Red 25
Sudan III	Solvent Red 23
Direct Green G	Direct Green 8
Celliton Blue Extra	Disperse Blue 1
Cerse Orange R	Solvent Orange 1
Alizarine Red S	Mordant Red 3
Alizarine Yellow R	Mordant Orange 1
Alcian Blue 8GX	Ingraint Blue 1
Victoria Blue R	Basic Blue II
Eriochrome Black T	Mordant Black 11
Ponceau 6R	Acid Red 44
Phloxin B	Acid Red 92
Phloxine	Acid Red 98
Patent Blue	Acid Blue 1
Bismark Brown G	Basic Brown 1
Savinyl Blue B	Solvent Blue 10

[0043] Group I compounds can be used individually or in mixtures.

[0044] The group of organic acidic compounds with a pK less than about four generally consists of organic acids or the halogenated sulphonphthaleins or both, which are soluble in the selected solvent, when the latter is in the liquid state. Examples of these acids include oxalic acid, maleic acid, dichloroacetic acid, trichloroacetic acid, 2-naphthalene-sulphonic acid, chloroanilic acid, bromophenol blue, bromothymol blue, chlorophenol red, bromochlorophenol blue, bromocresol green, 3,4,5,6-tetrabromophenol-sulphonphthalein, bromophenol red, chlorocresol green, chlorophenol blue, bromocresol purple and 2,4-dinitrobenzenesulphonic acid.

[0045] The group of basic dyes or basic indicators include the aminotriphenyl methanes, also known as the triaryl methanes, or their soluble salts, 8-hydroxyquinoline and the quinoline dyes, preferably the cyanines. Examples are: basic fuchsin, pinacyanol iodide, pinacyanol chloride, pinacyanol bromide, 2-p-(dimethylaminostyryl)-1-ethyl-pyridinium iodide, crystal violet, cryptocyanine, dicyanine A, 3,3'-diethylthiacarbocyanine iodide, 1,1'-diethyl-2,2'-cyanine iodide, ethyl red, quinaldine red, ethyl violet, brilliant green, pararosaniline, pararosaniline acetate, 8-hydroxy-quinoline, 1-ethylpyridinium iodide and 5-(p-dimethylaminobenzilidine) rhodanine. Preferably the weight of the acid compounds is about three or more times the weight of the basic compounds.

[0046] The above-mentioned pK values refer to the pK values as measured in water. Generally it is preferred that the pK of the acidic compound is lower than the corresponding pK value of the basic compound. Preferably the acid compounds have a pK value less than about four and the basic compounds have a pK value less than about 5.

[0047] It should be noted that when the basic compound consists solely of one or more aminotriphenylmethanes or their soluble salts, the acid compound should be selected from the group consisting of tetrahalogenated sulphonphthaleins and the other organic acids having a pK of less than about 2.

[0048] Preferred combinations of acidic compounds having a pK less than about 4 and basic dyes or basic indicators include bromophenol blue/basic fuchsin, chlorophenol blue/ethyl red and trichloracetic acid/3,3'-diethylthiadicarbocyanine iodide.

[0049] Mixtures of one or more organic acids having a pK less than about 2 and one or more acid dyes or acid indicators, used in the composition of matter, changes colour when the solvent passes from the solid into the liquid phase or reversed. In this combination the acid dyes used are preferably halogenated sulphonphthaleins.

[0050] Mixtures of one or more organic dyes, having a molecular structure containing a lactone group and one or more acids having a pK of about 8 to about 12, used in a solvent also change colour when the solvent passes from the solid phase onto the liquid phase or reversed. In that combination the preferred compounds are crystal violet lactone and one or more of acids such as phenol, bisphenol A, pyrocathechol or 3-nitrophenol.

[0051] The compositions of matter most preferably comprise (a) a suitable inert solvent as described above adapted to change from a solid state to a liquid state at substantially the predetermined temperature and (b) one or more organic moieties soluble in said solvent and adapted to change colour upon the change in state of the solvent at substantially the predetermined temperature when so dissolved, and selected from:

(1) one or more Group III compounds consisting of pinacyanol iodide, quinalidine red, 1,1'-diethyl-2,2'-cyanine iodide, pinacyanol chloride, thionin, methylene blue, cresol red, chlorophenol red, neutral red iodide, neutral red chloride, crystal violet, acridin orange, toluidin blue O, Orasol Orange RLN™, Orasol Navy Blue™, Irgalith Red PR™, Fat Red BS™, methyl violet, Xylene Cyanol FF™, Rhodamine B™, Rhodamine 6G™, Irgalith Magenta TCB™, Irgalith Pink TYNC™, Toluidin Blue O™, Savinyl Green B™, Savinyl Blue RS™, purpurin, 3,3'-diethylthiadicarbocyanine iodide, cryptocyanine, Dicyanine A, merocyanine 540, 4-(p-ethoxyphenylazo)-m-phenylene diamine monohydrochloride, Yellow Orange S™, Chrysidan G™, fuchsin, Aurintricarboxylic acid (ammonium salt), Victoria Blue R™, Pyronin G™, gallein phloxine, Erythrosin Yellow Blend™, chlorophenol blue, bromophenol blue, bromocresol purple, Coriphospine O™, acriflavine, acridine orange, rhoduline violet, Alizarin cyanin 2R™, Alizarin Red S™, alcannin, Aurantia, Direct Green G™, Fast Red Salt 3GL™, Fast Blue Salt BB™, Fast Garnet Salt GBC™, Carta Yellow G 180 o/o™, murexide, Savinyl Blue GLS™, Irgalith Blue GLSM™, phthalocyanine, Di Amingreen B™, Alizarian Blue S™, Celliton Blue Extra, neocyanine, Janus Green™, dimethyl yellow, Fast Yellow™, methyl red sodium salt, Alizarin yellow R™, Eriochrome black T™, Chromotrope 2R™, Ponceau 6R™, Brilliant Ponceau G/R/2R™, Chromolan yellow, Sudan Red B™, Bismarck Brown G™, Fat Black™, Resorcin Brown™, Benzofast pink 2BL™, Oil Red EGN™, Euroglaucine, Fuchsin NB™, parafuchsin, Patent Blue™, Irgalith Blue TNC™, Phloxin B™, fluorescein sodium salt, Rhodamine B base™, Eosinscarlet, Eosin Yellowish™, Erythrosin extra bluish, 4'5-dibromo fluorescein, ethyleosin, Phloxine™, Cyanovin B™, chlorocresol green, pinacyanol bromide, 2-p-dimethylaminostyryl)-1-1-ethyl pyridinium iodide, ethyl red, neutral red, iodide, nigrosine, Savinyl Blue B™, Orasol Blue BLN™, Safranin-O™, Azocarnum G™, Phenosafranine, Azocarmine BX™, Solophenyl Brilliant Blue BL™, Nile Blue A™, gallocyanine, Gallamine blue, celestine blue, methylene green, Azure A/B/C™, Blue VIF Organol™, Alizarin, Nitrofast Green GSB™, quinalizarine, Oil Blue N™, Solvay Purple™, Ciba Blue™, Indigo Synthetic™, Chromophtal Bordeaux RS™, Thiorifolex™, Acid Alizarin Red B™, 5-aminoflourescein, Rose Bengal™, Martius Yellow™, Chicago Blue 6B™, Alcian Blue 8GX™, cresyl violet, 4,4'Bis(dimethylamino) benzylhydrol, Zinc Pthalocyanine, Sudan III™, Pyronin Y™, Toluylene Blue™, cresyl violet perchlorate, Mendola's Blue™, Phosphine Dye™, Nitron™, cresyl violet acetate, ceres orange R™, 4-phenylazo-1-naphthyl-amine, 4-(4-dimethylamino-1-napthylazo)-3-methoxybenzene sulphonic acid, Bindschedler's Green™, and p-(p-dimethylaminophenylazo)benzoic acid (referred to below as the Group III compounds or Group III organic moieties), or

(2) a binary mixture of:

(A) one or more of a Group I body of compounds (referred to below as the Group I compounds) consisting of (a) the organic acids, which when inserted in the solvent system at conditions other than supersaturation will yield a colour change visible to the naked eye, and also have a pK of less than about four and (b) the halogenated sulphonphthaleins; and

(B) one or more of a Group II body of compounds (referred to below as the Group II compounds) consisting of the aminotriphenylmethanes and their soluble salts, 8-hydroxyquinoline, and the cyanines, with the proviso that if no Group III compound is present and if the Group II compounds must be selected from one or more of the group consisting of consist solely of one or more aminotriphenylmethanes or their soluble salts, then the Group I compound must be selected from one or more of the group consisting of oxalic acid, suitable sulphonic acids and the tetrahalogenated sulphonphthaleins, and other organic acids having a pK₁ of about or less than 2.

[0052] Of course, the primary application of the instant invention is where the change in state of the composition of matter is induced by temperature forces for use in a temperature indicating device. By "suitable sulphonic acids" is meant sulphonic acids soluble in the selected solvent; these may be, for example, benzene sulphonic acid, naphthalene sulphonic acid, toluene sulphonic acid, anthracene sulphonic acid, etc. depending on the solvent.

[0053] An interesting phenomenon exhibited by the compositions of the invention is illustrated by the example of a composition essentially consisting of pinacyanol iodide (at 0.035 weight percent) in ortho-bromonitrobenzene:ortho-chloronitrobenzene (75:25) solvent. In the liquid phase this composition is blue, and in the solid phase appears rose/tan. However, if the composition is chilled to a very low temperature at a very high rate of cooling initially, the colour of the solid appears purple. As the composition is allowed to warm to room temperature, the colour changes from purple to rose/tan, requiring about 3 to 5 minutes for the colour to become rose/tan. Similar phenomena have been observed with other compositions containing other Group III moieties or other Group I plus Group III combinations.

[0054] Another example of an especially preferred Group I compound is chlorophenol red at a concentration of about 0.05 percent by mass. When dissolved in a solvent such as OCNB/OBNB, dibenzofurane, para-toluic acid and other halogen nitrobenzenes, the liquid composition has a yellow colour.

[0055] As enumerated above, in the absence of one or more Group III compounds to be used for the organic moieties in the solvent system, one or more of a Group I body of compounds must be employed together with one or more of a Group II body of compounds. The Group I body of compounds generally consist of (a) the organic acids, which when inserted in the solvent system (at conditions other than supersaturation) will yield a colour change visible to the naked eye, and have a pK of less than about four, and (b) the halogenated sulphonphthaleins which are soluble in the selected weakly polar or nonpolar aromatic solvent described below. Preferably, the Group I compound has a pK of between zero and three, and most preferably between about zero and about two. Example of this Group I body of compounds include oxalic acid, naphthalenesulphonic acid, trichloroacetic acid, bromophenol blue, bromothymol blue, chlorophenol red, bromochlorophenol blue, bromocresol green, 3,4,5,6-tetrabromophenol sulphonphthalein, bromophenol red, and chlorocresol green. Some compounds, such as maleic acid, will work if soluble in the predetermined solvent system employed if the correct Group II compound is chosen.

[0056] These first groups of compounds, which are generally the halogenated sulphonphthaleins, are derivatives of the sulphonphthaleins in the following ways: first the unsubstituted compounds are diprotic acid/base indicators, each having pK values of (1) a pK₁ of about 2 and (2) a pK₂ of about 7 to about 9. The halogenated derivatives show only one pK which is much lower than the pK₂ of the unsubstituted sulphonphthalein. Because there are halogen substituents on the sulphonphthalein molecule, it is believed (without limitation of the invention) that the pK value is reduced and the acid strength of the Group I is increased. As a consequence of this, the halogenated derivatives will respond in combination with one or more of the Group II compounds enumerated below to produce the colour reaction. For example, in a OCNB-OBNB solvent system and in combination with basic fuchsin (a Group II material), bromochlorophenol blue (a Group I material) gives a green colour in the solid phase and a strikingly red colour in the liquid phase. This is very similar to the colour found when the bromophenol blue (a Group I compound) is combined with basic fuchsin in the same ortho-chloronitrobenzene: ortho-bromonitrobenzene solvent system.

[0057] It is believed that the Group II compounds, which are generally the aminotriphenylmethanes, their soluble salts, 8-hydroxyquinoline, and the cyanines, act as constituents which perform a "dye" function. Of course, as indicated by the disclosure above, a Group I compound may also act as a "dye" function. Examples of Group II compounds include ethyl red, crystal violet, pararosaniline (or "para Rosaniline Base"), pararosaniline acetate (or "para Rosaniline acetate"), basic fuchsin, 8-hydroxyquinoline, ethyl violet, brilliant green, pinacyanol chloride, and 3,3-diethylthiodicarbocyanine iodide. The Group I compounds are preferably selected from the group consisting of bromophenol blue, bromochlorophenol blue, and bromothymol blue. One will notice that the second group of compounds generally consist of dyes which have basic nitrogen groups either as substituent amines or in heterocyclic rings. In general, the addition of one or more of the first group of compounds along with the second group of compounds to a solution of the previously described nonpolar or weakly polar aromatic solvent(s) such as ortho-chloronitrobenzene and ortho-bromonitrobenzene solutions will provide a colour difference between the solid and liquid phases of the aromatic solvent. It is preferred that the total weight of the Group I and Group II compounds be about 0.025 to about 0.05 total weight percent of the entire weight of the composition of matter. It is advised that the melting point of the Group III or Group I and Group II moieties be more than the melting point of the solvent system. It is preferred that the melting point of each of the Group I and Group II constituents be substantially more than the melting point of the solvent system selected, and it is much preferred that these Group I and Group II compounds melt at more than sixty degrees above the melting point of the solvent system. A basic requirement is that at least one of the Group I and Group II compounds reflects or absorbs light in the visible area of the spectrum at or below the melting point of the solvent system or, in the alternative, at or above the melting point of the solvent system, or both, in different colours so that a change in colour is visible to the naked eye. It is also preferred that the Group I compounds weigh three or more times the weight of the Group II compounds. While 0.05 weight percent of the total of the Group I and Group II compounds or Group III compound(s) is most preferred, any effective amount from the smallest for which the change in colour is visible to the naked eye upon change in phases is satisfactory, and certainly no more than the solubility limits of the Group I and Group II compounds (or Group III compound(s)) in the solvent system at the melting point might also be affected. A supersaturated solution of Group I and Group II compounds (or Group III compound(s)) in the solvent system, is not preferred, since Group I-III compounds are substantially more expensive than the solvent system constituents and an excess of them will be extravagant. Any pressure may be employed in making or in using the composition(s) of matter in a temperature-indicating device so long as the solvent does not generate a substantial vapour in the application for the composition. If a Group III compound is not employed, it is preferred that the Group I compound has a lesser pK₁ and pK₂ value than the corresponding pK values of the Group II compound. Preferably, the Group II compound should have a pK₁ value of less than about 5, and the Group I compound should have a pK1 of less than about 4.

[0058] As it will be appreciated by those skilled in the art having access to this disclosure, it is possible with the disclosure given above to combine almost any Group I compound indicated pK, which is soluble in the solvent system selected, (a solvent system of ortho-bromonitrobenzene: ortho-chloronitrobenzene, for example) and a complementary acid base material from Group II and generate practically any desired change in colour. The considerations for those skilled in the art will be (1) the selection of Group III and/or Group I and Group II compound(s) which yield a satisfactory change in predetermined colours; (2) that these compounds are soluble in the solvent system in the liquid state; (3) that the solvent system be properly determined for the temperature range desired; (4) that the Group I and/or Group II compounds (or Group III compounds) be soluble in the desired system, and (5) if pertinent, that one compound of the Group I compounds react as a strong acid against one or more of the Group II compounds in the solvent system.

[0059] As it will be recognized by those skilled in the art having access to this disclosure, one may employ combinations of more than one Group III moiety, or a combinations of more than one Group III moiety, or a combination of a Group III moiety and a Group I moiety, or a combination of a Group II moiety and Group III moiety, or more than one Group I moiety with more than one Group II moiety to obtain colour shifts generally not found in a single system, e.g. a mixture of pinacyanol iodide and quinaldine red (two Group III compounds) yields a tan solid and deep dark purple liquid. There are some instances where two Group I compounds may be operable where one acts as an acid relative to the other e.g. (1) naphthalene sulphonic acid and one or more of (2) bromochlorophenol blue, chlorophenol blue, or bromocresol purple.

[0060] As an alternative to using one or more of the Group II compounds with one or more of the Group I compounds, one of the aforesaid Group III compounds can be selected, with (or preferably) in place of a combination of one or more Group I compounds and one or more Group II compounds. A caveat and proviso must be stated: in absence of a Group III compound one should employ one or more Group I compounds with one or more Group II compounds; if the Group II compounds consist solely of one or more aminotriphenylmethanes or their soluble salts, then the Group I compound should be from one or more of the group consisting of oxalic acid, suitable sulphonic acids, tetrahalogenated sulphonphthaleins, and other soluble strong organic acids having a pK₁ of about or less than 2.

[0061] Another example of a Group I compound and a Group II compound is bromophenol blue and basic fuchsin. In the solid form, the basic fuchsin behaved as if it were at a very low pH and was in a form which has a green colour between its pK₁ and pK₂. This green colour of basic fuchsin at very low pH is a little known fact, but can easily be demonstrated in any laboratory with common reagents. In the liquid form, however, the bromophenol blue is yellow. The basic fuchsin was not in its first acid form and became red. Thus, the colour of the liquid was red.

[0062] It will be appreciated that generally the colour of the liquid is the same or similar to the colour of the Group II compound or Group III compound when dissolved in the liquid phase of most of the suitable solvents employed.

[0063] Similarly, crystal violet, which is a pH indicator having a pK₁ of approximately 1, forms, in combination with oxalic acid and dissolved in the OCNB/OBNB solution, a blue liquid and a yellow solid.

[0064] It has also been found as well that (1) quinaldine red (a Group III compound) which has a pK₁ of approximately 1.6; (2) ethyl violet, which has a pK₁ of about 1.2; and (3) brilliant green, which has a pK₁ of about 1.4, all react in solutions with naphthalenesulphonic acid to form different coloured solid-then liquid-phases.

[0065] As alternative to the above for Group I-Group II combinations, when the Group I material is other than a simple acid, and is a "dye" compound (such as bromophenol blue), in addition to the Group I's behaviour as an acid, there may be formed in the composition aggregates, mixed polymers, and the like, which cause what is referred to in the literature as "metachromism" or "metachromacy". Metachromacy is that property of a substance which is expressed as a change in colour (according to the wavelength of the light in which it is viewed) due to an outside force. Metachromacy is mainly attributed to that colour change phenomenon when a dye is brought together with certain "tissue" molecules (macromolecules, e.g. solid materials such as heparin, polysaccharides). Certain organic dyestuffs, however, are characterized by different colours when dissolved in inert solvents, which is described as "solvatochromism" (see HACK'S CHEMICAL DICTIONARY 421 (4th Ed 1969)).

[0066] Once the organic moieties Group III compounds and/or Group I and Group II compounds are determined for the desired colour change, they are added to a liquid mixture of the solvent constituents for the predetermined temperature and mixed, preferably by any suitable industrial mechanical mixing means until a substantially complete dissolution has been obtained.

[0067] After the solvent weight fractions have been determined and the composition of matter formed for each of the increment temperatures to be tested, a suitable temperature-indicating device is constructed such as the device described below having a plurality of temperature-sensitive regions, preferably having cavities in a heat-conductive carrier such as aluminum in which each composition of matter corresponding to one of the preselected points along the temperature curve fills one of the regions, preferably a cavity, in the heat conductive carrier device. A method and apparatus for depositing precisely metered quantities of a temperature-sensitive composition of matter on a surface are disclosed in US-3810779. A suitable device for sealing a heat-sensitive transparent cover sheet means in vacuum-sealing engagement with an aluminum heat-conductive carrier over cavities in the carrier is the Webb Model No. 2 machine manufactured by Bio-Medical Sciences, Inc in Fairfield, New Jersey. The web machine embosses the heat conducting carrier means, fills the embossed cavities with thermally responsive material utilizing the fill system disclosed US-3810779, and lays down a transparent cover sheet in sealing engagement with the carrier means.

2. Temperature-Indicating Device

[0068] A temperature-indicator device is shown in Figure 1 comprising a flat, gradually curved, or substantially curvilinear heat-conducting carrier means having one or more spaced cavities defined herein to determine a like number of predetermined temperatures in a temperature range by means of a like number of different thermally-responsive composition of matter. Each of the predetermined temperatures is associated with a composition of matter that is substantially without impurities, and may or may not be the compositions of matter stated above, but a composition of matter which does change from an opaque form when solid to a transparent liquid upon melting. The temperature-indicating device comprises (1) a flat, gradually curved, or substantially curvilinear heat-conducting carrier with one or more cavities indented therein; (2) (in the absence of employing the compositions of matter of this invention) an indicator means located at the bottom of each of said cavities; (3) a transparent cover sheet means in sealing engagement with the carrier means above and overlying each of said cavities to form an enclosure between the walls of the cavity and the transparent cover sheet means; and (4) a composition of matter which substantially fills the cavity and is adapted to change from a solid to a liquid at substantially the predetermined temperature associated with said cavity.

[0069] As shown in Figure 1, the colorant 1 fills the bottom of a cavity "A" in a flat heat-conducting carrier means 2 of a certain thickness (indicated by arrows 6), the carrier means being substantially filled with a "classical" solid solution 5. The cavity "A" is covered by a transparent cover sheet means 4 which fits in sealing engagement with heat-conducting carrier means 2 immediately surrounding cavity "A" and covering the solid solution 5 filling cavity "A". Within the solid solution 5 is a substantially spherical cavity 3 which has a diameter only slightly smaller than the width 12 of the cavity minus the small width 11 of the colorant 1. In the embodiment shown in Figure 1, the cavity in the carrier means is in the shape of a trapezoid rotated around its axis, having a large diameter 8 at the top of the cavity and a smaller diameter 9 at the bottom of the cavity. The width 7 of the transparent film 4 is preferably substantially equal to the width 6 of the heat-conducting carrier means 2. While the exact dimensions (6, 7, 8, 9, 11, 12) of a cavity in items such as those in Figure 1 vary with the solvent system employed, the materials selected, and the composition of matter which is predetermined (whether or not one of the compositions of matter described above or a classical composition of matter which changes from opaque to transparent with change in phases from solid to liquid), it is well to describe a device employing ortho-chloronitrobenzene and ortho-bromonitrobenzene recently constructed.

[0070] As shown in Figure 1, the heat conducting carrier means 2 is an aluminum foil of thickness 6 of approximately .076 mm (0.003 inches). The heat-conducting carrier means 2 is preferably a material which as a high thermal conductivity and relatively large surface area of contact with the test subject and be of minimum thickness, while preserving its structural integrity, in order to permit rapid conduction of heat into the cavity such as shown in Figure 1. Where aluminum is used, its thickness may vary from about 0.025 mm (0.001 inches) to about 0.10 mm (0.004 inches). In a particularly effective embodiment, the heat-conducting carrier means may be made of plastic. The carrier is provided with the necessary strength to serve as the main structural support, while at the same time providing rapid and uniform temperature distribution throughout the thermometer device. As a consequence, the time required for taking temperature is substantially diminished. The depth 12 of the cavity "A" in the device shown in Figure 1 is selected to be preferably about 0.10 mm (0.004 inches), with the upper horizontal width 9 being approximately 0.89 mm (0.035 inches). The thickness 7 of the transparent film is approximately 0.025 mm (0.001 inches), the letter being a painted letter on the bottom of the cavity "A". As shown in Figure 1, a layer 1 of colorant material, such as a paint, is stamped onto the bottom of each cavity "A" of a visible material that may be somewhat absorbed into the composition of matter or solid solution 5 upon melting of the "classical" solid solution 5 to make the colorant material more visible.

[0071] The transparent film cover means 4 may be polypropylene, polyethyleneterephthalate (such as that sold under the trade mark Mylar), nitrocellulose, polyvinyl chloride, etc. As shown in Figure 1, the transparent film cover means 4 is preferably a thermoplastic material and can be a coextruded film of Nylon 6™ (manufactured by the Allied Chemical Company) and Surlyn 1652™ (manufactured by E I duPont de Nemours & Company) which film is produced by Pierson Industries Incorporated that is subsequently laminated to polypropylene by the Millprint Company of Milwaukee, Wisconsin.

[0072] In each cavity "A" in the device shown in Figure 1, one of the predetermined compositions of matter that is associated with a predetermined melting point is poured into the cavity, filling approximately 60% of said cavity. After partial filling of each cavity "A" with a particular composition of matter (here OCNB:OBNB) associated with a temperature to be measured (here between 35.3°C and 40.4°C (96.0°F and 104.8°F)), transparent film 4 is put in sealing engagement with aluminum foil 2 through the use of machine such as the Webb Model No. 2 manufactured by Bio-Medical Sciences Inc of Fairfield, New Jersey. Small deviations can be made in ratios of the dimensions 6 through 12, or alternatively, the ratios could be maintained for different sized systems (for example, by multiplying distances 6 through 12 by a uniform but different constant) without substantially affecting the performance of the device.

[0073] Figure 2 shows a partial plan view from above and the side of a known thermometer of the type disclosed in US-4232552, which includes a heat conducting carrier means "C" of a thermometer in a Celsius scale. In a particularly effective embodiment of this clinical thermometer, a rectangular grid is formed wherein each cavity 13 employs a construction as in Figure 1 and is clearly associated with a temperature to be determined within the range to be tested through markings located on the side of the grid.

[0074] Figures 3A and 3B show another known thermometer for measuring temperatures at 0.36°C (0.2°F) increments from 35.3°C to 40.4°C (96.0°F to 104.8°F), providing the compositions disclosed in US-4232552 patent (preferably OCNB:OBNB/pinacyanol iodide) in the cavities of the device shown in Figure 1.

[0075] Figure 3A shows a plan view of the substantially flat oral temperature indicting device as seen from above. Again, the thermometer has an aluminum heat conducting carrier means 44 (having a thickness indicated by the arrows 47 in Figure 3B) which acts not only as a main structural body of support, but at the same time provides rapid and uniform temperature distribution throughout the spatula portion "F" (having a width indicated by arrows 54 containing grid "G" of a plurality of cavities (each of diameter 57 and spaced centre-to- centre with each neighbour along a horizontal "x" axis or vertical "y" axis in Figure 3A at a distance 52 apart) of Figure 1, each cavity with the composition of matter and each associated with a predetermined temperature to be measured at 0.11°C (0.2°F) increments from 35.3°C to 40.4°C (96.0°F to 104.8°F). "Spatula" portion "F" of the device of Figure 3A is rounded for safety so that some distance (indicated by arrows 56) is maintained between the most forward row of cavities and the edge of the device. It will be observed that, if known compositions are employed instead of the compositions of the invention, each cavity will necessary employ an indicator layer such as the layer 1 in the device show in 1. It will be evident that an indicator layer is not required when the thermally responsive material is a solvent in combination with the organic moieties referred to in US-4232552.

[0076] The aluminum heat-conducting carrier means in the device shown in Figure 3A is covered above for the entire handle "E" portion by a top plastic layer 42 of width 54, preferable made out of a plastic such as polystyrene, polypropylene, or polyethylene.

[0077] The handle "E" has been stamped from below so as to make the device realize two ridges, ribs, or abutments 41a that protrude from above the carrier means 44 by some nominal distance which is approximately the same as width 47 of carrier means 44; likewise, the device realizes two cavities 41b in carrier means 44 that parallel the ridges 41a.

[0078] Although the distances shown in Figures 3A and 3B can be readily adjusted with respect to one another or in proportion (widths 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, and 58 can be multiplied by different constants). A preferred configuration of device suitable for measuring human temperatures in the range of 35.3°C to 40.4°C (96.0°F to 104.8°F), employing ortho-chloronitrobenzene and ortho-bromonitrobenzene in a solvent system with pinacyanol iodide in an amount of 0.035% by weight is described below, as sold by PyMaH Corporation (Somerville, New Jersey) under the trademark TEMPA DOT READY STRIP. Referring again to Figure 3A, the thermometer has a width 54 of about 87 mm (0.345 inches) at the widest portion of handle "E" and has the same width 54 in the spatula portion "F" of the thermometer. The cavities each have a diameter 57 of about 1 mm (0.039 inches) and each cavity has a depth of about 0.13 mm (0.005 inches), and is spaced from each neighbour on a horizontal "x" axis or vertical "y" axis by a distance 52 of 0.38 mm (0.015 inches). The top and bottom rows of cavities are of a distance 55 of about 1 mm (0.039 inches) from the leading edges, respectively, of the thermometer, and have a centre line on the right-hand column which is a distance 56 of about 4.9 mm (0.193 inches) from the tip of the rounded edge of the spatula "G" portion of the thermometer. Figure 3B is a section along line 13-13 of Figure 3A, and shows the oral thermometer device with an overall length of 10.8 cm (4.250 inches), and consists of an aluminum heat conducting carrier means 44 having an overall length of 10.8 cm (4.250 inches) and a depth 47 of about 0.08 mm (0.003 inches). The aluminum head conducting carrier means 44 is covered on the handle portion "E" of the thermometer by a polypropylene or polystyrene layer of thickness 48 of about 0.08 mm (0.003 inches); the carrier means also engages a polypropylene or polystyrene bottom plate mean 46 of width 49 of about 0.08 mm (0.003 inches) that traverses the entire length of the thermometer. Two bands of thermoplastic material (coextruded film of Nylon 6™ and Surlyn 1652™ subsequently laminated to polypropylene) cover the two sub-grids 37.8 to 40.4°C and 35.6 to 37.7°C (100 to 104.8°F and 96.0° to 99.8°F) and are each of width 51 of approximately 7.6 mm (0.300 inches) along the "x" axis and of depth 50 of from about 0.08 to 0.13 mm (0.003 to about 0.005 inches).

[0079] Figure 4 shows a cross-sectional view of a known disposable thermometer showing cavities in which are held the temperature indicating system 69. The heat conducting material 67 is covered by a transparent layer 66 by a polyisobutylene adhesive layer 68.

[0080] The indicating system of the present invention comprises a thermally sensitive material dispersed in a matrix forming material. The matrix forming material is an amorphous organic natural or synthetic polymeric material in which the thermally sensitive material is insoluble at the predetermined temperature at which it forms a liquid phase, and with respect to which it is inert. Any thermally sensitive material of the prior art may be utilized provided that it meets the above criteria with respect to the matrix forming material. The preferred thermally sensitive materials are the OCNB and OBNB referred to in US-4232552. More preferably the organic moiety disclosed in that document is utilized in conjunction with the OCNB and OBNB.

[0081] Illustrative non-limiting examples of matrix forming materials useful in the practice of this invention are polyisobutylene, low density polyethylene, amorphous polypropylene and microcrystalline waxes. The preferred matrix forming material is polyisobutylene. In its preferred form the matrix forming material has a number average molecular weight of about 2,500 to about 400,000, for example about 2,500 to about 75,000. The Parapol™ polyisobutylene typically has a viscosity of about 3,000 cs to about 4400 cs at 100°C, for example 3,500 to 4400 cs. Parapol 2500 has a typical number average molecular weight of about 2500 which corresponds to a viscosity of 4400 cs at 100°C. The temperature sensing composition of this invention comprises about 50 to about 75 weight percent of matrix forming material and about 25 to about 50 weight percent of a thermally responsive material. Where the thermally responsive material contains other compounds such as dyes, organic moieties as disclosed in US-4232552, nucleating agents etc, the weight percent of thermally responsive material includes such other compounds. Preferably the matrix forming material comprises about 60 to about 70 weight percent of the temperature sensing composition.

[0082] In a preferred embodiment, the OCNB and OBNB referred to in US-4232552 in combination with the organic moieties disclosed therein are utilized as the thermally responsive material. As is described in that document, a different composition of the solid solution is utilized for each temperature to be monitored. For a clinical thermometer this will generally cover the range of from about 35.3°C to about 40.4°C (96.0°F to 104.8°F). The thermally responsive material disclosed in US-4232552 (OCNB/OBNB) together with any other compounds is referred to as "TRM."

[0083] While a nucleating agent is not required in the practice of this invention its incorporation into the temperature sensing composition is preferred since it can reduce the time for reversal of the thermometer to its unfired state to about 3 to 4 minutes. Where the TRM comprises the thermally responsive materials disclosed in US-4232552, the preferred nucleating agent is anthraquinone. Preferable the anthraquinone is dispersed into a quantity of matrix forming material.

EXAMPLES

[0084] A thermometer was made using the thermally responsive solid solution disclosed in US-4232552 together with pinacyanol iodide as the organic material. The following formulation was utilized.

Component	wt %
Polyisobutylene (Exxon Parapol 2500)	60.0
TRM	33.3
9,10-anthraquinone in Parapol 2500 premix (2.5 wt %)	6.7

[0085] The following method of preparation was utilized:

1. The polyisobutylene and TRM are heated to about 49°C (120°F).

2. The TRM is dispersed in the polyisobutylene using mechanical mixing.

3. Continue mixing while the composition is cooled to room temperature and all of the TRM has solidified and been dispersed into the polyisobutylene.

4. Add the 9,10-anthraquinone premix to the cooled blend and disperse by mechanical mixing.

[0086] The above described temperature sensitive composition is utilized in preparing a clinical thermometer. The thermometers are held in a water bath maintained at the temperature to be tested for a time sufficient to completely melt the temperature sensing composition. Reading stability of about 30 minutes is achieved at room temperature. The reading stability time and reversal time can be controlled by altering the quantity of nucleating agent utilized. Instead of using a premix, by dispersing about 1% by weight anthraquinone into the PIB/TRM dispersion, the retention time of the stable reading is reduced to 30 seconds and the time for complete reversal of the thermometer is about 10 minutes at room temperature.

[0087] In another embodiment, the TRM is ground to reduce its particle size to about 80 to about 100 mesh (US Sieve Series). The TRM is the uniformly dispersed into the matrix material by mechanical mixing at a temperature below the melting pint of the TRM. The nucleating agent, or preferably the nucleating agent premix, is then added to the TRM in matrix material dispersion and mixed at a temperature below the melting point of the TRM until the nucleating agent is uniformly dispersed. The matrix forming material, for example a polyisobutylene, cannot be a solvent for the TRM, the dye dispersed in the TRM, or for the nucleating agent. Furthermore, it should be non-volatile and not be soluble in the TRM.

[0088] Any combination of TRM and matrix forming material which meet the required criteria can be used to prepared the thermometers of this invention. For taking the temperature of children, the thermometer can be used either as an axillary or rectal thermometer with appropriate adjustment of calibration to compensate for the difference in temperature indicated at such location other than the mouth as compared to body core temperature.

[0089] The term "temperature sensitive composition" as used in the specification means the combination of the matrix forming material and the thermally responsive material, and optionally, an indicator such as a dye or the organic moieties disclosed in US-4232552. The term "temperature responsive material" (TRM) as used in the specification means a normally solid compound or mixtures of compounds which is subject to a change of state from a solid to a liquid at a predetermined temperature within the temperature range to be monitored. The TRM should be susceptible to supercooling after it has changed from the solid to liquid state for at least a few minutes, generally several hours and as much as 24 hours.

[0090] The TRM can be emulsified into the polyisobutylene utilizing a dispersing or emulsifying agent to assist in reducing the particle size of the TRM. It is believed that the small particle size results in greater stability of the composition from the standpoint of settling out or coalescence of the TRM.

[0091] The preferred emulsifying agent is a C₁₄ to C₂₄ saturated alcohol, more preferably a C₁₆ to C₂₂ alcohol. Since the thermometers of this invention may be used orally, the dispersing or emulsifying agent of choice is cetyl alcohol because it is readily available as USP/NF grade. Other grades do not present a toxicity problem. However, utilizing a USP/NF grade avoids any question as to the compounds safety.

[0092] In this embodiment of the invention the polyisobutylene (PIB) to TRM ratio, by weight, is about 90/10 to about 66/34, preferably about 80/20 to about 75/25. The nucleating agent used in this composition is 9,10-anthraquinone utilized at about 0.01 to about 0.10 weight percent. The saturated alcohol is utilized at about 7 ppm to about 60 ppm, preferably about 8 ppm to about 50 ppm.

[0093] A typical formulation for use in the composition of the invention is as follows:

Component	Quantity
Polyisobutylene (Exxon Parapol 2500)	75.15 wt%
TRM	24.75 wt %
9,10-anthraquinone	0.099 wt %
cetyl alcohol	8.0 ppm

[0094] The cetyl alcohol is dissolved into the TRM prior to the emulsification step. A premix of the anthraquinone is prepared by mixing it with a minor amount of the polyisobutylene. The premix can comprise about 75 parts PIB to about 25 parts of anthraquinone to about 95 parts PIB to about 5 parts anthraquinone. Typically, the premix composition will comprise about 80/20 to about 90/10 parts of PIB to anthraquinone; preferably about 90/10 parts of PIB to anthraquinone by weight. The emulsification step can be carried out utilizing a high shear mixer. The TRM is liquefied by heating and added to the polyisobutylene and mixed in the high shear mixer for a time sufficient to fully emulsify the two components. The blend is subsequently cooled while mixing continuously. It has been found generally that a mixing time of about 5 to about 10 minutes is sufficient to emulsify the compositions fully. After the emulsification step is completed, the anthraquinone premix is added to the blend and mixing is continued for about 5 to about 10 minutes.

[0095] The appropriate mixing time will be a function of the high shear mixer selected as well as the batch size. Mixing times are readily determined without undue experimentation. In carrying out the emulsification step a ROSS planetary mixer (a one quart model LDM) was utilized. Initially, hot water at 60°C (140°F) was run through the jacket of the mixer. As mixing continued water temperature was decreased to maintain the batch temperature at about 60°C (140°F). Subsequently, after mixing was completed, cold water was run through the jacket to cool the mixture to about 4.4°C (40°F) to solidify the TRM. After warming the mixture to room temperature the anthraquinone premix comprising 90 parts PIB to 10 parts of anthraquinone was added in an amount sufficient to bring the anthraquinone concentration in the TRM/PIB blend to about 0.099% by weight, and mixing continued for about 10 minutes. The batch size utilized in the Model LDM blender was about 300 grams.

[0096] After preparation of the emulsified TRM/polyisobutylene mixture, the composition is passed through a 100 mesh screen to eliminate any particles of TRM which are greater than 0.1 mm (0.004 inches).

[0097] Surprisingly, the compositions of the reversible thermometer of this invention respond to more temperature rapidly to reach an equilibrium temperature reading as compared to the prior art thermometers disclosed in US-4232552 described above.

[0098] While the process is described as an emulsification process, it will be appreciated that the resulting product has a TRM dispersed into a matrix forming material which is insoluble in the TRM. Hence the composition of matter is substantially the same as that described above except that the particle size of the TRM has been reduced by utilizing the emulsification process.

Claims

1. A composition of matter suitable for use in a reversible thermometer comprising:

(a) a thermally responsive material capable of being supercooled at least for several minutes, and subject to a change in state from a solid to a liquid substantially at a predetermined temperature;

(b) means for visually observing the change in state; and

(c) a matrix forming material comprising an amorphous organic compound, the matrix forming material being insoluble in the thermally responsive material;

the thermally responsive material being dispersed within the matrix forming material, and the composition of matter being reversibly responsive to changes in temperature and remaining in the liquid state for a time sufficient to permit a user of the composition to observe the change in state.

2. A composition as claimed in claim 1, in which the matrix forming material comprises a polyisobutylene, low density polyethylene, amorphous polypropylene or mixtures thereof.

3. A composition as claimed in claim 1, in which the matrix forming material is polyisobutylene.

4. A composition as claimed in claim 1, in which the thermally responsive material together with the means for visually observing the change in state thereof exhibits a sharp colour change upon transition from a liquid state to a solid state or from a solid state to a liquid state, the thermally responsive material together with the means for visually observing the change in state comprising:

(a) a solvent which can provide a temperature responsive composition forming a solid solution in the solid state and is adapted to change from a solid to a liquid state substantially at a predetermined temperature; and

(b) an effective amount of at least one organic moiety dissolved in and inert towards the solvent, which is adapted to change the colour of the composition visible to the naked eye upon the change in state at substantially the predetermined temperature when so dissolved, thee organic moiety being selected from:

(1) at least one of a Group III body of compounds consisting of pinacyanol iodide, quinaldine red, 1,1'-diethyl-2,2'-cyanine iodide, pinacyanol chloride, thionin, methylene blue, cresol red, chlorophenol red, neutral red iodide, neutral red chloride, crystal violet, acridin orange, Toluidin Blue O™, Orasol Orange RLN™, Orasol Navy Blue™, Irgalith Red PR™, Fat Red BS™, methyl violet, Xylene Cyanol FF™, Rhodamine 6G™, Rhodanine B™, Irgalith Magenta TCB™, irgalite pink TYNC™, Toluidine Blue O, Savinyl Green B™, Savinyl Blue RS™, purpurin 3,3'-diethylthiadicarbocyanine iodide, cryptocyanine, Dicyanine-A™, Merocyanine 540™, 4-(p-ethoxyphenylazo)-m-phenylene diamine monohydrochloride, Yellow Orange S™, Chrysoidin-G™, fuchsin, aurintricarboxylic acid (ammonium salt), Victoria Blue R™, Pyronin G™, gallein, phloxine, Erythrosin Yellow Blend™, chlorophenol blue, bromophenol blue, bromocresol purple, Coriphosphine O™, acriflavine, acridine orange, rhoduline violet, Alizarin Cyanin 2R™, Alizarin Red S™, alcannin, Aurantia, Direct Green G™, Fast Red Salt 3GL™, Fast Blue Salt BB™, Fast Garnet Salt GBC™, Carta Yellow G 180 o/o™, murexide, Savinyl Blue GLS™, Irgalith Blue GLSM™, phthalocyanine, Di Amingreen B™, Alizarin Blue S, Celliton Blue Extra™, neocyanine, Janus Green, dimethyl yellow, Fast Yellow, Methyl red sodium salt, Alizarin yellow R™, Eriochrome Black T™, Chromotrope 2R™, Ponceau 6R™, Brilliant Ponceau G/R/2R™, chromolan yellow, Sudan Red B™, Bismarck brown G™, Fat Black™, Resorcin Brown™, Benzofast pink 2BL™, Oil Red EGN™, Euroglaucine, Fuchsin NB™, parafuchsin, Patent Blue™, Irgalith Blue TNC™, Phloxin B™, fluorescein sodium salt, Rhodamine B base™, Eosin Scarlet, Esoin Yellowish™, Erythrosin extra bluish, 4,5-dibromoflucorescein, ethyleosin, Phloxine™, Cyanovin B™, chlorocresol green, pinacyanol bromide, 2-(p-dimethylaminostyryl)-1-ethyl pryidinium iodide ethyl red, neutral red iodide, nigrosine, savinyl blue B™, Orasol Blue BLN™, Safranin O™, Azocarnun G™, Phenosafranine, Azocarmine BX™, Solophenyl Brilliant Blue BL™, Nile Blue A™, gallocyanine, gallamine blue, celestine blue, methylene green, Azure A/B/C™, Blue VIF Organol™, Alizarin, Nitrofast Green GSB™, quinalizarine, Oil Blue N™, Solvay purple, Ciba Blue™, Indigo synthetic™, Chromophtal Bordeaux RS™, Thiorifolex™, Acid Alizarin Red B™, 5-Aminoflourescein, Rose Bengal™, Martius Yellow™, Chicago Blue 6B™, Alcian Blue 8GX™, Cresyl violet, 4,4' Bis(dimethylamino)-benzylhdrol, Zinc Pthalocyanine, Sudan III™, Pyronin Y™, Toluylene Blue™, cresyl violet perchlorate, Mendola's Blue™, Phosphine Dye, Nitron™, cresyl violet acetate, Ceres Orange R™, 4-phenylazo-1-naphtylamine, 4-(4-dimethylamino-1-napthylazo)-3-methoxybenzene sulfonic acid, Bindschedler's Green™, and p-(p-dimethylaminophenylazo) benzoic acid;

(2) a binary mixture of:

(A) at least one of a Group I body of compounds soluble in said solvent consisting of the halogenated sulphonphthaleins and the organic acids having a pK₁ of less than or about four;
and

(B) at least one of a Group II body of compounds consisting of the aminotriphenylmethane and their soluble salts, 8-hydroxyquinoline, and the cyanines;
with the proviso that if the Group II compounds consist solely of at least one aminotriphenylmethanes or their soluble salts, then the Group I compound must be selected from at least one of the group consisting of oxalic acid, suitable soluble sulfonic acids and the tetrahalogenated sulphonphthaleins, and the other soluble organic acids having a pK₁ of less than or about 2, and in which the weight ratio of the Group I body of compounds to the Group II body of compounds is more than or about 3 to 1; and

(3) at least one of the aforesaid Group III body of compounds with at least one of the Group I or Group II bodies of compounds.

5. A composition as claimed in claim 4, in which the solvent is a weakly polar or non-polar aromatic compound comprising one or more of o-chloronitrobenzene, o-bromonitrobenzene, metaiodonitrobenzene, para-iodonitrobenzene and para-toluic acid.

6. A composition as claimed in claim 4, in which the solvent is a solid solution of o-chloronitrobenzene and o-bromonitrobenzene.

7. A composition as claimed in claim 4, in which the organic moiety comprises an effective amount of a mixture of ethyl red and bromophenol red dissolved in the solvent and subject to a colour change upon a change in state of the solvent at a predetermined temperature.

8. A composition as claimed in claim 4, in which the organic moiety comprises an effective amount of a mixture of ethyl red and bromocresolpurple dissolved in the solvent and subject to a colour change upon a change in state of the solvent at a predetermined temperature.

9. A composition as claimed in claim 4, in which the organic moiety comprises an effective amount of pinacyanol iodide dissolved in the solvent and subject to a colour change upon a change in state of the solvent at a predetermined temperature.

10. A composition as claimed in claim 4, in which the organic moiety comprises an effective amount of a mixture of ethyl red and bromophenol blue dissolved in the solvent and subject to a colour change upon a change in state of the solvent at a predetermined temperature.

11. A composition as claimed in claim 1, which includes a nucleating agent by which the time required for the composition to revert to the solid state after being removed from a heat source for causing the thermally responsive material to undergo a change in state can be reduced.

12. A composition as claimed in claim 11, in which the nucleating agent comprises 9,10-anthraquinone.

13. A composition as claimed in claim 11, in which the solvent is a solid solution of o-chloronitrobenzene and o-bromonitrobenzene and the nucleating agent is anthraquinone.

14. A composition as claimed in claim 1, in which an emulsifier is included in the thermally responsive material.

15. A composition as claimed in claim 1, in which the emulsifier is a C₁₄ to C₂₄ saturated alcohol, preferably a C₁₆ to C₂₂ saturated alcohol, especially cetyl alcohol.

16. A temperature indicating device which comprises a heat conducting carrier having a multiplicity of spaced regions defined therein to determine a like number of predetermined temperatures in a predetermined temperature range, the spaced regions containing a like number of different compositions of matter therein, the carrier having a transparent cover sheet means in sealing engagement therewith, the compositions of matter being as claimed in any one of claims 1 to 15.

16. A process of dispersing the thermally responsive material in the matrix forming material of a composition as claimed in any one of claims 1 to 14, which comprises the steps of:

(a) converting the thermally responsive material to a liquid by heating it above the predetermined temperature;

(b) emulsifying the thermally responsive material into the matrix forming material by mechanical shearing, thereby forming an emulsion of thermally responsive material in the matrix forming material; and

(c) cooling the mixture of thermally responsive material and matrix forming material sufficiently to solidify the thermally responsive material.

17. A process as claimed in claim 16, in which the temperature of the mixture of thermally responsive material and matrix forming material is adjusted to room temperature before adding the nucleating agent.

Drawing